Recently, CMOS (Complementary Metal Oxide Semiconductor) image sensors are spotlighted as next-generation image sensors. The CMOS image sensor is a device employing a switching mode to sequentially detect an output of each unit pixel by means of MOS transistors, in which the MOS transistors are formed on a semiconductor substrate corresponding to the unit pixels through a CMOS technology using peripheral devices, such as a controller and a signal processor. The CMOS image sensor includes a photodiode and the MOS transistor in each unit pixel, and sequentially detects electric signals of each unit pixel in a switching mode to realize images.
Since the CMOS image sensor is manufactured by utilizing the CMOS technique, it has an advantage of low power consumption. In addition, since a smaller number of photo-processing steps are required, the manufacturing process of the CMOS image sensor can be simplified, Further, since a controller, a signal processor, an analog/digital converter, and the like can be integrated on a CMOS image sensor chip, the CMOS image sensor can minimize the size of a product. Accordingly, the CMOS image sensor is widely applied to various application fields, such as a digital still camera and a digital video camera.